<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

</body>
<script>
    /*var a=0.1;
     var b=0.2;
     var c=a+b;
     if(c == 0.3){
     document.write("666")
     }else{
     document.write("垃圾")
     }*/
    var a = 123;
    fn(a);//fn(123)
    function fn(a) {
        // var a = 123;
        a = 456;
        return a;
    }
    alert(a);
</script>
</html>